Biological Evolution II Flashcards
Name the types of species concepts.
- Biological
- Ecological
- Morphological
- Genetic
- Phylogenetic
What is the biological species concept?
Species is a group of populations whose members have the potential to interbreed in nature and produce viable and fertile offspring.
State the advantages of the biological species concept.
- Considers reproductive compatability.
State the limitations of the biological species concept.
- Not applicable to asexually reproducing species. (prokaryotes)
- Not applicable to self fertilising species. (hermaphrodites)
- Exceptions where hybrid individuals are both viable and fertile.
What is the ecological species concept?
Species is a group of organisms exploiting the same ecological niche - role of species in an ecosystem.
State the advantages of the ecological species concept.
- Can be applied to asexual and sexual organisms.
- Useful in distinguishing bacterial species (same species of bacterial cells use same types of nutrients etc)
State the limitations of the ecological species concept.
- Difficult to determine degree of competition between different members of the same species.
- Does not consider morphology and reproductive compatability.
What is the morphological species concept?
Species is a group of organisms that are similar in morphology/anatomy.
State the advantages of the morphological species concept.
- Can be applied to asexual and sexual organisms.
State the limitations of the morphological species concept.
- Morphology of members of the same species may look different while members of different species may look similar.
- Subjectivity in deciding number and type of morphological traits to compare.
- Subjectivity in determining differences in a morphological trait that exhibits continuous variation.
What is the genetic species concept?
Species is a group of genetically compatible interbreeding natural populations that is genetically isolated from other such groups.
How are species identified using the genetic species concept?
Coding and non-coding genetic data from nuclear and mitochondrial genomes to identify species and species boundaries.
State the advantages of the genetic species concept.
- Applies to individuals from different known species which are able to interbreed and produce viable and fertile offspring. (genetically isolated but not reproductively isolated)
State the limitations of the genetic species concept.
- Difficulty in determining degree of genetic differences required to indicate separate species.
- Subjectivity in determining degree of difference.
What is the phylogenetic species concept?
Species is the smallest group of organisms that share a common ancestor, forming one branch on the phylogenetic tree.
How are species identified using the phylogenetic species concept?
Tracing of phylogenetic history of a species by comparing its characteristics with other organisms to distinguish groups of different species.
State the advantages of the phylogenetic species concept.
- Applies to asexual and sexual organisms.
State the limitations of the phylogenetic species concept.
- Difficulty in determining degree of differences required to indicate separate species.
Which species concepts could you apply to both asexual and sexual species?
- All except biological species concept.
- They define species on the basis of characteristics rather than ability to reproduce.
Which species concept would be the most useful for identifying species in the field? Explain.
- Morphological species concept.
- It is based only on the appearance of the organism.
How do new species form?
- Species form as gene pools become separated and require reproductive barriers that impede gene flow between two populations.
- Different mutations arise independently and change accumulates in each isolated population.
- Inidividuals become reproductively isolated over a period of time and no longer able to mate to produce fertile viable offspring.
State the types of speciation processes.
- Allopatric speciation.
- Sympatric speciation.
What is allopatric speciation?
Speciation results from existence of physical or geographical barrier.
What is sympatric speciation?
Speciation occurs in populations that live in the same geographical location and results from physiological or behavioural differences.
What is the difference between allopatric and sympatric speciation?
Allopatric speciation results from existence of geographical barrier (different locations) but sympatric speciation occurs for populations that live in the same geographical location.
[Speciation] Explain geographical isolation. (allopatric speciation)
- Different populations separated from each other due to physical barriers.
- Fertile individuals from different populations no longer able to mate with each other. (absence of gene flow)
- Results in two distinct gene pools.
- Different selection pressures acting on organisms, accumulation of independent mutations, genetic drift alters allele frequencies.
- Overtime, genetic differences increase, unable to mate to form fertile viable offspring, leads to speciation.
[Speciation] Explain behavioural/physiological isolation. (sympatric speciation)
- Different populations separated from each other due to physiological or behavioural differences.
- Fertile individuals from different populations less able to mate with each other. (reduced gene flow)
- Eventually results in two distinct gene pools.
- Accumulation of independent mutations, genetic drift alters allele frequencies.
- Overtime, genetic differences increase, unable to mate to form fertile viable offspring, leads to speciation.
Define biological classification.
Classification is the organisation of species according to particular shared characteristics. It does not take into consideration evolutionary relationship between the species.
Define phylogeny.
Phylogeny is the organisation of species according to particular characteristics which takes into consideration the evolutionary relationship between the species.
What is the difference between biological classification and phylogeny?
Biological classification does not take into consideration evolutionary relationship between the species but phylogeny does.
State the limitations of classification.
Grouping based on similarities can be misleading due to:
* Presence of analogous structures.
* Related organisms can look different due to adaptation to different environments.
* Taxanomic ranks are not equivalent across the kingdoms.
* Does not take into account evolutionary relationships.
[Molecular Homology] Explain the importance of the use of genome sequences in recontructing phylogenetic relationships.
- When ancestors give rise to descendants, descendants exhibit high overall similarity in their DNA
- Descendants evolve independently, accumulate more differences in DNA due to mutations.
- Distantly related species accumulate a greater number of evolutionary differences, closely related species share a greater portion of DNA.
- Can be shown by alignment of amino acid sequences.
Describe the advantages of using mtDNA compared to nuclear DNA.
- Maternal Inheritance
mtDNA is passed down the maternal line and does not undergo any recombination in meiosis unlike nuclear genome –> any differences are only due to mutations accumulating, making it easier to establish point of divergence between mtDNA of species –> trace maternal lineages more easily - Higher mutation rate
Mutations accumulate faster in mtDNA due to lack of protective histones in mtDNA to wrap around and limited DNA repair mechanisms –> more differences in DNA arises - Present in abundance
- Small genome size
- Highly conserved genes
mtDNA contains sequences that are highly conserved across many different species as they code for proteins essential for respiration in aerobic organisms.
Describe the advantages of using molecular methods.
- Applicable to all organisms
Genetic code is universal and all organisms possess nucleic acids and proteins that can be studied in all living organisms. - Abundance of data
Genome contains huge amounts of data and provide large pool of information about evolution - Quantifiable
Molecular methods are an objective assessment of how closely related species are and is open to statistical analysis. - Study of homologies that are not observable
Helps to analyse evolutionary relationships between species that cannot be determined via comparing morphology alone. - Used to construct phylogeny for species without fossil records
- Provide a better basis of comparison than morphology, esp. between species with similar morphological structures
